Standardized color measurement is very important in a wide variety of applications, ranging from quality control to chemical analysis. In addition, some instruments provide relative color measurements by comparing the target to a known standard. Consequently, reliable color measurements require periodic calibration of any given instrument for reflection measurement using a working color standard. General properties of reflection standards are discussed in Erb, "Requirements for Reflection Standards and the Measurement of their Reflection Value", J. Applied Optics, Vol. 14, No. 2, February 1975.
Two types of color standard are commonly used; a glossy standard and a matte standard. Advantageously, a glossy standard includes a glossy surface having a protective layer which desirably protects the standard and permits the standard to be cleaned without impairing the properties of the glossy surface. Unfortunately, however, specular reflections occur with a glossy standard due to the hard protective layer. The specular reflections can affect the measured value obtained and, therefore, a diffuse matte color standard is often preferred, if not required, for any given application.
Heretofore known matte reflection standards have been made by applying a matte pigment to a substrate. The reflectance of the matte pigment is directly measured from that surface One such matte color standard is discussed in Color in Business, Science and Industry, Judd and Wyszecki, John Wiley & Sons, Inc., 250 (3d Ed. 1975). There, Judd and Wyszecki disclose color chips prepared by applying a pigmented matte film to a clear cellulose acetate base . The pigmented film side constitutes the matte side of the standard and the same matte coating serves as a glossy color standard when viewed through the clear, transparent acetate.
Unfortunately, matte pigment surfaces are subject to contamination since there is no hard protective layer, as there is in the case of a glossy finish. To the contrary, the matte pigment particles are located at the exposed surface and are subject to wear. Since a working standard is handled frequently during ordinary use, contamination gradually accumulates on a matte pigment surface and alters the reflections of the standard. As a further disadvantage, attempts to clean the surface of the unprotected matte finish result in a phenomenon known as polishing. That is, as the matte surface is cleaned it is gradually buffed and smoothed, thereby changing the reflectance of the surface. Thus, depending upon the care of the user matte standards can degrade dramatically and cannot be adequately and/or reliably cleaned in order to restore the standard to its original reflectance.
Therefore, it is one object of the present invention to provide a color reflection standard.
Another object of the present invention is to provide a matte reflectance color standard that is less susceptible to contamination and which can be cleaned without impairing the value of the matte surface as a reflection standard.
Yet another object of the present invention is to provide a matte reflectance color standard that is not susceptible to the effects of polishing.
Another object of the present invention is to provide a convenient matte and glossy reflection standard having matte and glossy surfaces which are less susceptible to contamination and which can be cleaned without polishing effects.
These and other highly desirable and unusual results are accomplished by the present invention in a convenient, contamination-resistant, cleanable working color standard.
Objects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be learned by practice with the invention, which is realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.
The invention consists of the novel parts, constructions, arrangements, combinations, steps, and improvements herein shown and described.